Cos(4x +π/4)=-√2/2, 4x+π/4= +-3π/4 +2πk, k∈Z,
1) 4x+π/4=3π/4 +2πk, 4x=2π/4+2πk, 4x=π/2+2πk, x=π/8+πk/2,
x∈[-π;π),
при к=0, x=π/8,
при к=1, x=π/8+π/2=5π/8,
при к=-1, x=π/8-π/2=-3π/8,
при к=-2, x=π/8-π=-7π/8.
2) 4x+π/4=-3π/4 +2πk, 4x=-π+2πк, x=-π/4+πk/2,
x∈[-π;π),
при к=0, x=-π/4,
при к=1, x=-π/4+π/2=π/4,
при к=2, x=-π/4+π=3π/4,
при к=-1, x=-π/4-π/2=-3π/4,